FR3091209A1 - AUTOMOTIVE STRUCTURE - Google Patents

Abstract

AUTOMOTIVE STRUCTURE The invention relates to a structure (1) of an electric or hybrid vehicle comprising a floor (3), a battery tray (4) fixed under the floor (3), and a plate (2) of compressed foam disposed between the battery tray (4) and the floor (3). The invention also relates to a vehicle comprising such a structure (1) and to an assembly method. Figure for abstract: 1

Description

Description

Title of the invention: AUTOMOTIVE STRUCTURE

The invention relates to a motor vehicle structure. The invention also relates to a vehicle comprising such a structure and a method of assembling such a structure.

Vehicles and in particular motor vehicles are subjected to vibrations. In order to improve the comfort of these vehicles, it is necessary to reduce these vibrations, which in particular generate noise.

We know the document US2008 / 136110A1 describing a sound insulation system between the vehicle floor and the energy tank, whether it is a fuel tank or a battery tray. The space between the fuel tank and the floor is insulated with an acoustic seal to prevent the transmission of noise into the sealed void space.

However, this solution provides partial insulation against noise but does not provide insulation against vibration.

The object of the invention is to provide a vehicle structure which overcomes the above drawbacks. In particular, the invention makes it possible to produce a vehicle structure which is simple and easy to implement and which allows insulation against the noise and vibrations of the floor of a vehicle.

The invention relates to an electric or hybrid vehicle structure comprising a floor, a battery tray fixed under the floor, and a compressed foam plate placed between the battery tray and the floor.

In one embodiment, the surface of the foam plate comprises microscopic perforations configured for the evacuation of air contained in the foam during compression of the plate and / or configured to prevent the entry of water in the foam.

In one embodiment, the foam plate further comprises a hole opening on one of its faces or crossing it from one face to the other, configured for the evacuation of air contained in the foam during compression of the plate.

In one embodiment, the foam plate further comprises a portion positioned towards the rear of the vehicle, the surface of which comprises holes configured for the evacuation of air contained in the foam during compression of the plate .

In one embodiment, the foam plate is compressed between the floor and the battery tray according to a compression ratio of between 20% inclusive and 40% inclusive, in particular between 30% inclusive and 40% inclusive.

In one embodiment, the thickness of the compressed foam plate is between 10 mm inclusive and 20 mm inclusive, preferably between 13 mm inclusive and 14 mm inclusive, in particular equal or substantially equal to 13 mm with a 30% compression ratio of the plate.

In one embodiment, the foam plate comprises a polyurethane foam.

In one embodiment, the foam is a cell foam having dimensions less than 2 mm.

The invention also relates to a vehicle, in particular an electric motor vehicle or a hybrid vehicle, comprising a structure according to the invention.

The invention finally relates to a method of assembling a vehicle structure comprising a step of perforating a foam plate, a step of arranging the foam plate between a vehicle floor and a battery tray vehicle, a step of compressing said foam plate at a compression rate between 20% and 40% and a step of fixing the battery tray to the floor so that the foam plate remains compressed at a rate of compression between 20% and 40%.

The accompanying drawings show, by way of example, an embodiment of a vehicle structure according to the invention.

[Fig.l]

Figure 1 shows a vehicle structure.

[Fig.2]

Figure 2 shows a vehicle structure.

[Fig.3A]

FIG. 3A represents a foam plate seen from above according to a first embodiment optimizing the evacuation of the air.

[Fig.3B]

FIG. 3B represents a foam plate seen from above according to a second embodiment optimizing the evacuation of the air.

[Fig.3C]

FIG. 3C represents a foam plate seen from above according to a third embodiment optimizing the evacuation of the air.

[Fig.4]

Figure 4 is an exploded view of a vehicle structure according to an embodiment of the invention.

An example of a vehicle structure according to an embodiment of the invention is described below with reference to Figure 1.

The structure 1 comprises a vehicle floor 3, and a battery tray 4. The battery tray 4 is fixed to the floor 3. In particular, the battery tray is fixed below the floor 3. By "in- below ”means here that the battery tray 4 is below the floor 3 when the vehicle comprising the structure is in the operating position. The battery tray 4 is therefore preferably intended to be placed outside the passenger compartment of the vehicle.

The vehicle structure 1 also includes a plate 2 of foam. The foam plate 2 is disposed between the battery tray 4 and the floor 3 of the vehicle structure 1.

The floor 3 advantageously constitutes a horizontal platform of the passenger compartment of the vehicle.

The floor 3 is not limited to the first layer inside the passenger compartment of the vehicle but may include several layers or an assembly of which at least one layer is disposed on the interior surface of the vehicle.

The battery tray 4 may include at least a portion of parallelepipedal or substantially parallelepipedal shape.

As illustrated in Figure 2, the battery tray 4 includes a battery 43. The battery 43 is preferably electrically connected to an electric motor for driving the vehicle. In one embodiment, the battery tray 4 comprises a cooling system 42. The cooling system 42 is preferably placed below the battery 43.

The battery tray 4 also includes a rack or an envelope intended to contain the battery and the cooling system. An upper side 41 of the rack is in contact with the foam plate 2 or is oriented towards the foam plate 2.

The foam plate 2 comprises a width and a length significantly greater than the thickness of said foam plate 2. The foam plate 2 therefore preferably comprises two main faces separated by a smaller dimension, called the thickness.

By "significantly greater" is meant that the width and the length are at least 10 times greater than the thickness, preferably at least 50 times.

The foam plate 2 is a plate 2 of solid foam. The foam plate 2 comprises a porous or cellular material. The porous material comprises a solid matrix with fine geometry saturated by a fluid. The porous material preferably comprises a solid continuous network in which air bubbles are trapped.

Preferably, the foam plate 2 comprises a polymer foam.

The polymer foam advantageously makes it possible to obtain a plate 2 of foam.

Preferably, the foam plate 2 comprises a polymer matrix, very preferably a polyurethane matrix.

The foam plate 2 may include flame retardant compounds. Thus, the foam plate 2 can also serve as a fire barrier between the battery tray 4 and the floor 3 of the structure 1 of the vehicle.

The porous or cell material can be defined by its density and by the structure of the matrix, in particular by its porosity and by the shape of its cells or cells.

The loss factor (or internal damping module) of the porous material can be between 0.1 and 0.3 at a frequency of 10Hz and at a temperature of 23 ° C. The loss factor is a measure of the ratio of energy dissipated by damping to elastic energy retained and then returned during a deformation cycle.

The loss factor is equal to the tangent of the ratio between the loss module on the conservation module (E ’).

The compression conservation module (E ’) of the porous material can be between 1000 and 50,000 Pa at a frequency of 10 Hz and at a temperature of 23 ° C.

The density of the porous material can be between 20 and 100 g / L.

Preferably, the foam plate 2 comprises a microporous material, that is to say that the size of the cells or cells of the network is between 1 μm and 1 mm.

In one embodiment, the foam is a cell foam and the cells have dimensions less than 2 mm.

The foam plate 2 disposed between the floor 3 and the battery tray 4 is compressed or prestressed. Indeed, compression of the foam plate 2 advantageously allows better absorption of floor vibration 3 and noise. Compression increases the rigidity of the plate.

In one embodiment, the foam plate 2 is compressed by forces orthogonal to the two main faces or is compressed so as to reduce the thickness of the foam plate 2.

The battery tray 4 can be mechanically fixed to the floor 3 so as to leave a space (between the battery tray and the floor 3) less than the thickness of the plate 2 of foam at rest, that is ie in the absence of stress exerted on the plate. In this way, the foam plate 2 is deformed during assembly by the compression provided by the floor 3 and the upper side 41 of the battery tray 4.

The vehicle structure may include fixing means so as to be able to fix the battery tray 4 to the floor 3. These fixing means preferably allow fixing without passing through the plate 2 of foam.

In one embodiment, the compression ratio of the foam plate 2 is between 20% and 60%. The compression ratio of the foam plate 2 is preferably around 30%. By "compression ratio" is meant the ratio of the difference between the thickness of the plate 2 of foam at rest and the thickness of the plate 2 of compressed foam divided by the thickness of the plate 2 of foam at rest .

The foam plate 2 may comprise a thickness of between 10 mm and 20 mm when it is compressed between the floor 3 and the battery tray 4. Preferably, the foam plate 2 comprises a thickness of approximately 20 mm at rest. Once the structure is assembled, said foam plate 2 is compressed by about 30%. Thus, the thickness of the foam plate 2 once compressed and mounted between the floor 3 and the battery tray 4 is approximately 13 mm.

The foam plate 2 also includes means for evacuating the air included in the solid matrix. These air evacuation means make it possible to evacuate the air from the foam plate 2 during its compression. This exhaust air reduces the risk of the plate 2 bursting during compression due to the air overpressure.

In a first embodiment illustrated in Figure 3A, at least one surface of the foam plate 2 comprises microperforations. The surface comprising the microperforations is preferably an upper surface of the foam plate 2. The exhaust air is then not hindered by the surface of the floor 3 or the battery tray 4.

The microperforations extend over a portion of the volume of the foam plate 2. Thus, the air trapped in the network of the solid matrix can more easily leave this matrix by passing through these perforations.

The microperforations can have a thickness or a diameter of between 0.05 mm and 3 mm. The microperforations can extend in the volume of the foam plate 2 over a length of between 20% and 99% of the length or width of the foam plate 2.

In one embodiment, at least one microperforations passing right through the plate 2 of foam over its length or across its width.

The foam plate 2 can comprise a density of microperforations of between 2 and 10 microperforations per mm ² , preferably between 2 and 6 microperforations per mm ² .

These characteristics of microperforations advantageously allow better evacuation of the air contained in the foam during compression of the plate and makes it possible to prevent the entry of water into the foam.

The microperforation can be positioned on both sides of the plate 2, preferably only one of the two faces is microperforated, this face must be positioned on the upper surface of the plate 2, that is, towards the passenger compartment of the vehicle (in contact with the floor of the automobile structure).

In a second embodiment illustrated in Figure 3B, the foam plate 2 comprises at least one through hole 7 on at least one main face, in particular a hole 7 passing through the thickness of the plate. The through hole 7 makes it possible to shorten the minimum distance to be traveled for the air to exit from the foam plate 2.

If the foam plate 2 comprises a single through hole 7, said through hole 7 is preferably located in a central area of the foam plate 2.

In one embodiment, the area of the opening of the through hole 7 is less than 5% or less than 1% of the area of the plate 2 of foam intended to come into contact against the battery tray 4 or the area of the foam plate 2 intended to come into contact against the floor 3.

In the embodiment where the foam plate 2 comprises several through holes 7, the sum of the areas of the orifices of the through holes 7 is less than 20% or less than 10% of the area of the foam plate 2 intended to come into contact against the battery tray 4 or the area of the foam plate 2 intended to come into contact against the floor 3.

The second embodiment described above can also be combined with the first embodiment.

In a third embodiment illustrated in FIG. 3C, compatible with the first and / or the second embodiment, the foam plate 2 comprises a portion located towards the rear of the vehicle, the surface of which includes holes 8 for the air evacuation.

Indeed, the positioning of the holes 8 of larger diameter in the rear area allows to evacuate a larger volume of air. This solution is particularly effective in the case where microperforations do not allow a sufficient volume of air to be evacuated in a relatively short time. of durability.

The risk of an air overpressure in the heart of the matrix is thus limited.

Thus, the assembly comprising the battery tray 4 and the foam plate 2 under the floor 3 create a mass-spring-mass effect.

The vibrations in the wall of the battery tray 4 and the sound waves are damped in the spring (the plate 2 of foam). Finally, sound and vibrations are dampened.

In one embodiment, the battery tray 4 comprises at least one fixing zone 6. The at least one fixing zone 6 can extend laterally relative to the upper side 4L

The upper side 41 can be arranged so as to leave a space (between the battery tray 4 and the floor 3) for the insertion of the plate 2 of foam as described above.

The at least one fixing zone 6 can comprise fixing means such as bores or tapped holes for fixing the battery tray 4 to the floor 3.

The invention also relates to a vehicle comprising such a structure 1. The vehicle is preferably a motor vehicle, very preferably a motor vehicle comprising an electric motor for driving the vehicle.

The invention also relates to a method of assembling a vehicle structure 1. An embodiment of an assembly process is described below. The vehicle structure 1 is preferably a vehicle structure 1 as described above.

The method comprises the following steps:

- the arrangement of a foam plate 2 between a vehicle floor 3 and a battery tray 4;

- Compression of said foam plate 2 at a compression ratio of between 20% and 40%;

- the fixing of the battery tray 4 to the floor 3 so that the battery tray 4 and the floor 3 are separated by a distance less than the thickness of the plate 2 of foam at rest.

Preferably, said distance is between 60% and 80% of the thickness of the plate 2 of foam at rest.

In one embodiment, the compression and fixing steps are carried out at the same time.

By "approximately" followed by a numerical value, is meant in the present application a range at more or less 10% of said numerical value.

Claims (1)

Claims [Claim 1] Structure (1) of an electric or hybrid vehicle comprising a floor (3), a battery tray (4) fixed under the floor (3), and a plate (2) of compressed foam disposed between the battery tray (4) and the floor (3). [Claim 2] Vehicle structure (1) according to the preceding claim, in which the surface of the foam plate (2) comprises microscopic perforations configured for the evacuation of air contained in the foam during compression of the plate and / or configured for avoid water entering the foam. [Claim 3] Vehicle structure (1) according to one of the preceding claims, in which the foam plate (2) further comprises a hole (7) opening on one of its faces or crossing it from one face to the other, configured for the evacuation of air contained in the foam during the compression of the plate. [Claim 4] Vehicle structure (1) according to one of the preceding claims, in which the foam plate (2) further comprises a portion positioned towards the rear of the vehicle, the surface of which comprises holes (8) configured for the evacuation of air contained in the foam during compression of the plate. [Claim 5] Vehicle structure (1) according to one of the preceding claims, in which the foam plate (2) is compressed between the floor (3) and the battery tray (4) according to a compression ratio of between 20% inclusive and 40 % included, especially between 30% included and 40% included. [Claim 6] Vehicle structure (1) according to one of the preceding claims, in which the thickness of the compressed foam plate (2) is between 10 mm inclusive and 20 mm inclusive, preferably between 13 mm inclusive and 14 mm inclusive, in particular equal or substantially equal to 13 mm with a compression ratio of 30% of the plate. [Claim 7] Vehicle structure (1) according to one of the preceding claims, in which the foam plate (2) comprises polyurethane foam. [Claim 8] Vehicle structure (1) according to one of the preceding claims, in which the foam is a cellular foam having dimensions of less than 2 mm. [Claim 9] Vehicle (5), in particular electric motor vehicle or hybrid vehicle, comprising a structure (1) according to one of the preceding claims. [Claim 10] Method for assembling a vehicle structure (1) comprising the following steps: • the perforation of a foam plate (2); • the arrangement of the foam plate (2) between a vehicle floor (3) and a vehicle battery box (4); • compression of said foam plate (2) at a compression ratio of between 20% and 40%; • fixing the battery tray (4) to the floor (3) so that the foam plate (2) remains compressed at a compression ratio between 20% and 40%.